Metals such as aluminum and their alloys have many uses in aerospace, commercial, and private industries. However, these metals have a propensity to corrode rapidly in the presence of water due to their low oxidation-reduction (redox) potential, thus significantly limiting the useful life of objects made from these metals, and/or increasing maintenance costs. These metals also may have a problem with paint adhesion, as the surface of the metal, when formed into an object, is generally very smooth.
The oxidation and degradation of metals used in aerospace, commercial, and private industries are serious and costly problems. To prevent the oxidation and degradation of the metals used in these applications; a protective coating can be applied to the metal surface. This protective coating may be the only coating applied to the metal, or other coatings can be applied to further protect the metal surface. In order to provide proper adhesion of coatings to the substrate surface and to provide corrosion resistance to the metal substrate, the substrate can be cleaned prior to application of the coatings. Typical cleaners may include alkaline based cleaners, which remove greases, oils, waxes and dirt from the metal surface. Acid cleaning/etching may also or alternatively be performed to remove metal oxides (e.g., rust, smut, etc.) and make the metal surface chemically active for the next finishing step.
Conventional cleaners can often produce smut when the substrate is cleaned, provide poor or inadequate adhesion of subsequent coatings, require the use of multiple steps and extensive periods of time to clean the substrate, require commercially unattractive steps, such as additional rinsing, deoxidizing, and/or sealing steps, and/or require the use of elevated temperature solutions. Multiple step cleaning processes add to the cost of metal finishing and increase environmental pollution. Therefore, an alkaline metal cleaner which does not produce smut, is effective in increasing adhesion of subsequent coatings in the metal finishing process, does not require multiple steps for application, and/or can be applied at room temperature would be desirable.